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Method and Structure to Bridge Current Return Path Discontinuities on Adjacent Reference Planes Within an Electronic Package

IP.com Disclosure Number: IPCOM000031877D
Original Publication Date: 2004-Oct-15
Included in the Prior Art Database: 2004-Oct-15
Document File: 6 page(s) / 85K

Publishing Venue

IBM

Abstract

A reference plane providing a current return path for high-speed signals may have openings which cause return path deviations. A return path bridge as described here could be constructed to minimize this return path deviation.

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Method and Structure to Bridge Current Return Path Discontinuities on Adjacent Reference Planes Within an Electronic Package

Electronic packages containing high-speed signalling typically provide reference planes in close proximity to signal traces. The signal return path normally follows the nearest portion of the adjacent reference plane or planes. A return path discontinuity occurs whenever the reference plane shape changes along the path of the signal trace. Many features inside an electronic package, such as vias, pads, voltage splits, and the corresponding openings associated with any of these items, may cause return path discontinuities. The current method to check for and minimize these return path discontinuities is through a visual or automated inspection of the design and modification of the wiring to minimize the effects of the discontinuity. The drawback of this method becomes apparent when the wiring constraints limit the length of the wire and any modifications to the wire will violate these constraints. A method and structure is need that preserves the wiring constraints and minimizes the return path discontinuity.

     The method and structure described here identifies a means to bridge a current return path discontinuity while maintaining the intended wire lengths. This method uses a return path bridge on the same plane as the signal itself to cross the discontinuity. The discontinuities are identified by either a visual inspection or a systematic computer-automated review of the design file data. The method for identifying return path discontinuities may be automated, and some of the discontinuities have methods and structures for minimizing signal return paths by modifying the referenc...